Acquired immunodeficiency syndrome (AIDS) and malaria are among the most devastating infectious diseases that have ever affected mankind, causing approximately five million deaths per year in the world. The effects of these diseases are most pronounced in underdeveloped countries in that the diseases are accompanied by financial and living conditions that are already miserable to start with. Several resource-poor countries cannot afford effective therapies that might allow the prevention of many deaths. The difficulties per se in treating both AIDS and malaria, caused in part by the drug-resistance of both their etiological agents, i.e., the human immunodeficiency viruses (HIV) and protozoa belonging to the genus Plasmodium, become exaggerated when the pharmaceutical weapons are extremely limited. In several resource-poor countries with high rates of HIV seroprevalence, the use of highly active antiretroviral therapy (HAART) has encountered major obstacles due to its high costs and the complexities of its prescription. Recently, due to humanitarian considerations, anti-HIV drugs have been offered at reduced prices to some of the least developed countries with a high HIV seroprevalence. The problem is, however, still far from being solved. Compared to antiretrovirals, antimalarials have lower costs, which may in any case weigh heavily on the budgets of several poorer countries. Chloroquine (CQ), recommended for a long time by the World Health Organization (WHO) as a first line treatment of malaria, is still the most affordable and widely adopted antimalarial option in Africa; however, the continuous emergence of drug-resistant Plasmodium strains renders its administration ineffective in a large number of areas in Africa, Latin America and South-Eastern Asia.
As most of the areas heavily stricken by AIDS also exhibit endemic malaria (and frequently individuals are co-infected), it would be useful to develop a treatment effective against both diseases.
In this regard, CQ may be particularly useful in that it has been demonstrated to exhibit in-vitro activity against HIV-1 replication and against several AIDS-related opportunistic microorganisms. It also has well-documented, long-term safety when used in immunocompromised individuals, (including those with HIV/AIDS), when dosed for antimalarial prophylaxis and in the treatment of rheumatic diseases. Although no information is available on the in-vivo effects of CQ on viral load, its hydroxy-analog hydroxychloroquine (HCQ) has proven in-vivo anti-HIV-1 activity. The anti-HIV activity of CQ is due to an impairment of the infectivity of virions produced by cells treated with the drug. Although the present invention is not limited to any particular mechanism, it is believed that the mechanism behind this inhibitory effect is inhibition of gp120 glycosylation. This hypothesis is supported by results showing that CQ impairs the formation of the heavily glycosylated epitope 2G12, which is located on the gp120 envelope glycoprotein surface and is fundamental for virus infectivity. These effects show that CQ inhibits viral replication by a mechanism different than those of currently used antiretroviral drugs, and this new mechanism has led to testing CQ in combination with antiretrovirals in clinical trials.
More detailed information on the anti-HIV effects of CQ can be found in the following two articles, which are hereby incorporated in the present patent application in their entirety:    Savarino A, Gennero L, Chen H C, Serrano D, Malavasi F, Boelaert J R, Sperber K. Anti-HIV effects of chloroquine: mechanisms of inhibition and spectrum of activity. AIDS Nov. 23, 2001; 15(17):2221-9.    Savarino A, Gennero L, Sperber K, Boelaert J R. The anti-HIV-1 activity of chloroquine. J Clin Virol 2001 February;20(3):131-5.
It is known that CQ may exert additive effects when associated with other anti-HIV drugs such as ddI, hydroxyurea, and AZT. The effects of a combinatorial administration of CQ and inhibitors (PIs) of the HIV protease (SEQ ID NO: 1) have however been totally unknown until the present invention. In view of the future large-scale administration of PI-based regimens in malaria-endemic areas, this interaction may provide the following: 1) CQ/HCQ and PIs are the only drugs tested in humans that inhibit HIV replication at a post-integrational stage; 2) the effects of both CQ and PIs result in an impairment of the infectivity of newly produced virions; 3) both CQ and PIs are substrates of and, at varying levels, inhibit important cell surface drug transporters, ie., the P-glycoprotein (P-gp) and the multi-drug resistance-associated proteins (MRP), which belong to the ATP-binding cassette family and modulate the intracellular concentrations of antiretroviral drugs. Of note, recent data indicate that CQ is capable of increasing the level of inhibition of P-gp- and MRP-mediated efflux exerted by PIs in CD4+ lymphocytes (Savarino et al., JAIDS 2004, in press).
The inhibitory effects of PIs on cell surface drug transporters may make the combination of CQ and a PI particularly useful in treatment of malaria.
Drug transport on the cell surface has been hypothesized to be involved in plasmodial drug-resistance. This theory is supported by several pieces of evidence.
First, a glycoprotein of P. falciparum, namely Pf-MDR, presents a high degree of homology with human P-gp and may be in some ways related to CQ-resistance. Ward S A, Bray P G. Definitive proof for a role of pfmdr 1 in quinoline resistance in Plasmodium falciparum. Drug Resist Updat 2000 April;3(2):80-81
Second, CQ-resistance in vitro is characteristically reverted by verapamil, a known inhibitor of the ATP-binding cassette in human cells. Sidhu A B, Verdier-Pinard D, Fidock D A. Chloroquine resistance in Plasmodium falciparum malaria parasites conferred by pfcrt mutations. Science Oct. 4, 2002;298(5591):210-3
Third, erythrocytes parasited by CQ-resistant P. falciparum strains accumulate more limited intracellular CQ pools than those parasited by CQ-sensitive strains. The capacity of a P. falciparum strain to decrease CQ accumulation within erythrocytes is strictly associated with mutations in a gene (Pf-crt) that encodes the so-called CQ-resistance transport (CRT) protein. The precise mechanisms by which P. falciparum CRT intervenes in these phenomena have not been elucidated yet. Of note, these mutations are present in the vast majority of the CQ-resistant field isolates of P. falciparum coming from different areas of the world and are not present in CQ-sensitive isolates. Sidhu A B, Verdier-Pinard D, Fidock D A. Chloroquine resistance in Plasmodium falciparum malaria parasites conferred by pfcrt mutations. Science Oct. 4, 2002;298(5591):210-3.
It would be beneficial to have compositions and treatments using a combination of CQ and a PI that inhibits both HIV and Plasmodium sp.